1. Field
The present disclosure relates generally to persistent surveillance. More particularly, the present disclosure relates to a method and apparatus for controlling the routing of a set of sensor platforms performing persistent surveillance of an area of interest using a dynamic visibility map of the area of interest.
2. Background
Persistent surveillance is surveillance that is performed over an area of interest over a prolonged period of time. Persistent surveillance may also be referred to as persistent intelligence, surveillance, and reconnaissance (ISR). Persistent surveillance may be performed using different types of imaging systems. These imaging systems may be attached to platforms, such as unmanned aerial vehicles (UAVs).
For example, a group of unmanned aerial vehicles having attached imaging systems may be flown over an area of interest to monitor the area of interest for a selected period of time. The imaging system attached to each of the group of unmanned aerial vehicles may have a field of view that covers at least a portion of the area of interest. However, depending on the type of area being monitored, each imaging system may not have a direct line of sight to the portion of the area of interest within its field of view. For example, terrain features, such as hills and mountains, may obstruct the line of sight from an imaging system to the surface of the area. Similarly, when the area of interest is an urban area, urban features such as buildings, man-made structures, bridges, antenna towers, and other types of features may obstruct the line of sight from an imaging system to the surface of the area.
Further, depending on the positioning of the group of unmanned aerial vehicles, not all of the area of interest may be visible to at least one of the group of unmanned aerial vehicles at any given point in time. Consequently, surveillance of the area of interest may not be as thorough as desired.
Some currently available methods for coordinating a group of sensor platforms may rely on predetermined search patterns. These predetermined search patterns may include, for example, without limitation, a creeping line pattern, a sector search pattern, a spiral pattern, and a square pattern. However, with these types of methods, surveillance may be constrained to a definite period of time—the time it takes to complete a particular predetermined search pattern. Further, these types of currently available methods may not allow for sensor platforms to join in and leave the group of sensor platforms performing the surveillance over time. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.